Prior art mechanical devices are often limited to treating a narrow range of vessel diameters and a certain type of obstruction. However, the diameter and the nature of the obstruction often varies along the diseased vessel, requiring multiple sizes and different kinds of prior art devices in a single clinical case. Furthermore, each of such prior art devices can be slow, traumatic and expensive. For example, a number of prior art devices comprise an abrasive tip with a spherical cross section, mounted on a rotating shaft to grind the obstructions to very small particles that can pass through the capillary blood vessels. Due to the small size of the particles, these devices have to be rotated at high speeds (e.g., 200,000 revolutions per minute) to grind the entire obstruction material in a reasonable time. In some of these devices, the tip is eccentrically mounted on the shaft and some of these devices use aspiration to try to remove the particles. However, as the abrasive tip of these devices grinds through a small vessel or through a hard obstruction material, even if the tip is mounted eccentrically on the shaft, it is forced to rotate in an opening that is not larger than the tip, which the tip essentially blocks. This prevents aspiration and cooling fluid or drugs from reaching the sides and the distal end of the tip, which may quickly cause thermal injury and/or perforation of the vessel wall.
A different commonly used method to open obstructed blood vessels consists of bringing clot-dissolving drugs (e.g., thrombolytic drugs such as streptokinase, urokinase, tPA and the like) into contact with the obstruction. However such drugs may take a long time, especially in the case of a long obstruction. Thus, catheters, which deliver and mix the drug with the obstruction material to accelerate the process, are available (e.g., Trellis System sold by Covidien Co., Mansfield, Mass.), but such systems are relatively cumbersome, expensive and address primarily soft obstructions.